Apparatus and method for radial and angular or rotational analysis or images for shape content and matching

ABSTRACT

A segmented radial spatial light modulator has an active optic area comprising a plurality of radially extending active optic modulators disposed at various angular orientations with respect to a central axis. The segmented radial spatial light modulator is used in separating and isolating portions of Fourier transform optic patterns from images for characterization of images by shape for recording, storing, retrieving, searching, and comparison to other images for matches and near matches. The images can be ghosted to increase optical power in the Fourier transform optic pattern without adding new shape content and for grading comparisons to other image shape characteristics for identifying near matches in addition to matches.

CROSS REFERENCE TO RELATED PATENT APPLICATION

This patent application is a continuation-in-part of U.S. patentapplication Ser. No. 10/051,364, filed in the U.S. Patent and TrademarkOffice on Jan. 18, 2002 now abandoned, which is a continuation in-partof U.S. patent application Ser. No. 09/536,426, filed in the U.S. Patentand Trademark Office on Mar. 27, 2000 now U.S. Pat. No. 6,678,411.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to spatial light modulators and, moreparticularly, to a spatial light modulator with radially oriented activelight modulating sectors for radial and angular analysis of beams oflight, including Fourier transform optic patterns, for uses such ascharacterizing, searching, matching or identifying shape content ofimages.

2. State of the Prior Art

There are situations in which useful information can be derived fromspatially dispersed portions of light beams. In particular, when animage is being carried or propagated by a light beam, it may be usefulto gather and use or analyze information from a particular portion ofthe image, such as from a particular portion of a cross-section of abeam that is carrying an image.

For example, in my co-pending U.S. patent application, Ser. No.09/536,426, which is incorporated herein by reference, narrow, radiallyoriented portions of a Fourier transform of an image are captured anddetected in the spatial domain and used to characterize and encodeimages by shape for storage, searching, and retrieval. As explainedtherein, such radially oriented, angularly or rationally spaced portionsof light energy from a Fourier transform, i.e., Fourier domain, of animage are captured sequentially in the spatial domain by positioning arotating, opaque mask or wheel with a radially oriented slit in theFourier transform domain of a light beam carrying the image afterpassing the light beam through a Fourier transform lens and detectingthe light in the spatial domain that passes through the slit at variousangular orientations, i.e., degrees of rotation. The light energydetected in the spatial domain that is passed through the slit in theFourier domain at each angular orientation is characteristic of theportions of the image content that are generally linearly aligned in thesame angular orientation as the slit in the rotating mask when the lightenergy is detected.

That system with the rotating, radially oriented, slit does perform thetask of characterizing and encoding images by shape content of theimages quite well and quite efficiently. However, it still has severalshortcomings. For example, resolution of spatial frequency of an imageat each angular orientation of the rotating slit is not as good as someapplications or uses of such a system might require. Also, the spinningmask or wheel with an associated drive mechanism, like all mechanicaldevices, has stability and long term reliability issues, not to mentionsize and weight requirements.

SUMMARY OF THE INVENTION

Accordingly, it is a general object of this invention to provide animproved apparatus and method for capturing and recording opticalinformation from portions of optical images.

A more specific object of this invention is to provide an improvedapparatus and method for spatial analysis of Fourier transform opticalpatterns of images for shape content of such images.

Another specific object of this invention is to provide an improvedapparatus and method for characterizing and encoding images by shapecontent for storing, searching, comparing, matching, or identifyingimages.

This and other objects, advantages, and novel features of the inventionshall be set forth in part in the description that follows, and in partwill become apparent to those skilled in the art upon examination of thefollowing description or may be learned by the practice of theinvention. The objects and the advantages may be realized and attainedby means of the instrumentalities and in combinations particularlypointed out in the appended claims.

To further achieve the foregoing objects, the apparatus of thisinvention includes a spatial light modulator with a plurality ofaddressable, active optic elements that extend radially at variousangular orientations in relation to an axis. The active optic elementsare preferably shaped to modulate portions of light beams incident ondiscrete sectors of an active optic area on which the beam of light canbe focused. Therefore, active optic modulators in the shape ofindividual sectors, i.e., essentially wedge-shaped, are preferred,although other shapes are also feasible and, in special circumstances,possibly even more desirable, such as rectangular for better resolutionor curved for detection of curved shape content of an image. For betterresolution of spatial frequency of shape content, the radially extendingwedges or rectangles of the active optic area can be comprised ofindividually addressable segments, which can be activated separately orin groups, depending on the resolution desires. Wedge-shaped sectors cancomprise segments of smaller, truncated wedge-shaped active opticelements or groups of sensors in pixel arrays that, in composite, formsuch shapes. Rectangular areas can also comprise smaller rectangularsegments or composited groups of sensors in pixel arrays to form suchradially extending, angularly spaced, active optic components or areas.For shape content characterization of an image, an optic pattern that isa Fourier transform of the image is focused on the active optic area,and radially disposed portions of the Fourier transform optic pattern atvarious angular orientations are selected and isolated by the spatiallight modulator and projected into the spatial domain for detection ofshape content of the image that is aligned with such angularorientations. The intensities of light detected from such respectiveportions are characteristic of such shape content, including brightness,sharpness, orientation, and density or spatial frequency of imagefeatures, and can be recorded, stored, or used to compare with similarlyanalyzed shape content of other images to find and identify matches ornear matches of images with such shape content. Optional imagepre-processing to add ghost images at various radial and angularrelationships to the image and at various light intensities can enhancedetectability of shape content and can enable near matching of imageswith similar shape content.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthe specification, illustrate the preferred embodiments of the presentinvention, and together with the descriptions serve to explain theprinciples of the invention.

In the Drawings:

FIG. 1 is an isometric view of a segmented radial spatial lightmodulation device according to this invention illustrated with a beam oflight focused on the light modulating components in the active opticarea of the device;

FIG. 2 is a front elevation view of the preferred light modulatingcomponents in the active optic area of the segmented radial spatiallight modulator device of this invention in the shape of segmentedmodulator sectors that are oriented to extend radially at variousangular orientations in relation to a central axis;

FIG. 3 is an enlarged, front elevation view of one sector of the active,light modulating components of the segmented radial spatial lightmodulator device;

FIG. 4 is a cross-sectional view of a portion of an active optic sectorof a segmented radial spatial light modulator of the present inventiontaken substantially along section line 4—4 of FIG. 3;

FIG. 5 is a schematic diagram of an optical image characterizer in whicha segmented radial optical analyzer device according to this inventionis illustrated in an application for characterizing and encoding opticalimages by shape content to exemplify its structure and functionalcapabilities;

FIGS. 6 a–c is an example spatial-domain image with large squares, whichis optically filtered in the Fourier transform domain according to thisinvention to produce example spatial domain images of low spatialfrequency vertical and horizontal shape content;

FIGS. 7 a–c is an example spatial domain image with small squares, whichis optically filtered in the Fourier transform domain according to thisinvention to produce example spatial domain images of high spatialfrequency vertical and horizontal shape content;

FIG. 8 illustrates a blank spatial domain image resulting from actuationof a segment or sector in the Fourier transform plane that has noincident light energy, this no shape content;

FIG. 9 illustrates the active optic segmented sectors of a preferredembodiment segmented radial spatial light modulator to facilitateexplanation of the spatial optic filtering of the example images inFIGS. 6 a–c and 7 a–c;

FIGS 10 a–c include diagrammatic, elevation view of the active lightmodulating components of the segmented radial spatial light modulatordevice to illustrate a use of an outer segment of a vertically orientedsector of the light modulation components of the segmented radialspatial light modulator device of this invention along with diagrammaticviews of an image being characterized and a resulting detectable opticpattern that is characteristic of some of the vertically oriented shapecontent of the image;

FIGS. 11 a–c include diagrammatic, elevation views similar to FIGS. 10a–c, but illustrating a use of a near inner segment of the verticalsector;

FIGS. 12 a–b include diagrammatic, elevation views similar to FIGS. 10a–c, but illustrating a use of a near outer segment of an active opticsector that is oriented 45 degrees from vertical;

FIGS. 13 a–c include diagrammatic, elevation views similar to FIGS. 10a–c, but illustrating a use of the outer segment of the horizontaloriented active optic sector;

FIGS. 14 a–c include diagrammatic, elevation views similar to FIGS. 10a–c, but illustrating a use of the outer segment of the active opticsector that is oriented 191.25 degrees from vertical;

FIG. 15 is a diagrammatic elevation view similar to FIG. 10 a, butillustrating a modified embodiment in which the active optic segmentsare rectangular instead of wedge-shaped;

FIG. 16 is a diagrammatic elevation view of another embodiment in whichgroups of individually addressable light sensors in a pixel array ofsensors can be activated together in locations that simulate sectors orsegments of sectors to achieve angular and/or spatial analysis of alight beam for characterization of an image by shape content accordingto this invention;

FIG. 17 is a cross-section view similar to FIG. 4, but illustrating amodification in which a modulated light beam passes through, instead ofbeing reflected by, a segmented radial spatial light modulator inaccordance with this invention;

FIGS. 18 a–c illustrates an optional ghosting technique for enhancingoptical power transmission to improve shape information detectioncapability and to provide graded shape content characterization toenable identification of near matches of shape content in variousimages; and

FIGS. 19 a–c illustrate the ghosting technique of FIGS. 18 a–c appliedto a slightly more complex image.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A segmented radial spatial light modulator (SLM) device 50 according tothe present invention is illustrated diagrammatically in FIG. 1 with abeam of light 27(p) focused on the active optic area 54 in the centerportion of the segmented radial SLM device 50. As illustrateddiagrammatically in FIG. 1, the segmented radial SLM device 50 ispreferably, but not necessarily, constructed as an integrated circuit 52mounted on a chip 56 equipped with a plurality of electrical pins 58configured to be plugged into a correspondingly configured receptacle(not shown) on a printed circuit board (not shown). In such a preferredembodiment, the pins 58 are connected electrically by a plurality ofwires 59 soldered to contact pads 55 of the integrated circuit 52 toenable addressing and operating optic components in the active opticarea 54, as will be discussed in more detail below.

An enlarged elevation view of the active optic area 54 of the integratedcircuit 52 is illustrated in FIG. 2, and an even more enlarged view ofthe active optic segments 502, 504, 506, 508 of one modulator sector 500(sometimes hereinafter “sector” for convenience) of the active opticarea 54 is illustrated in FIG. 3. Essentially, the segmented radial SLMdevice 50 is capable of selectively isolating radially disposed portionsof the incident light energy at various angular orientations in relationto a central axis 40 for detection, as will be explained in more detailbelow. One way of accomplishing such isolation is by reflecting, as wellas rotating plane of polarization of, the selected radially disposedportions of the light beam 27(p) that is incident on the active opticarea 54, while other portions of the light beam 27(p) are reflected, butwithout rotation of the plane of polarization, or vice versa. In thepreferred embodiment, each of the active optic segments, such assegments 502, 504, 506, 508 of sector 500 in FIG. 3, are addressableindividually through electrically conductive traces 503, 505, 507, 509,respectively, although the invention also can be implemented, albeitwith less spatial frequency or scale resolution, by a sector 500comprising only one active optic modulator or by activating one or moreof the individual segments simultaneously.

The selection and isolation of a portion of the incident light beam27(p) is illustrated in FIG. 4, which is a partial cross-section ofactive optic segments 506, 508. An incident light beam 27(p), which isdesignated, for examples as being p-polarized, i.e., polarized in thep-plane, will be reflected by, and will emerge from, segment 508 ass-polarized light 27(s), i.e., light polarized in the s-plane, or viceversa, when the segment 508 is activated by a voltage V on trace 509,while the unactivated segment 506 reflects, but does not rotate plane ofpolarization of, the incident light 27(p). In FIG. 4, the lightreflected by the activated segment 508 is designated as 61(s) toindicate its s-plane polarization, while light reflected by thenon-activated segment 506 is designated as 61(p) to indicate its p-planepolarization. The structure and function of the segments 506, 508, whichare typical of all the segments of all the sectors 500, 510, 520, 530,540, 550, 560, 570, 580, 590, 600, 610, 620, 630, 640, 650 of the activeoptic area 54, will be explained in more detail below. Suffice it to sayat this point that a s-polarization plane is orthogonal to, i.e.,rotated 90° in relation to, a p-polarization plane and that suchrotation of plane of polarization of a portion of an incident light beam27 or vice versa, (p) (see FIGS. 1 and 4) to s-polarization 61(s) (seeFIG. 4), while simultaneously leaving other portions of the incidentbeam 27(p) unrotated in the reflection 61(p), enables filtration orseparation of that portion 61(s) from the remainder of the light beam61(p), or vice versa, as will be explained in more detail below. Ofcourse, as mentioned above, incident beam 27 could be s-polarized, andthe device 52 could rotate a portion of such an incident beam top-polarization to enable filtration or separation. Such alternatives areall readily understood by persons skilled in the art as effectiveequivalents, and this invention does not require or prefer one of suchalternatives over others. Therefore, for simplicity, one or several ofsuch alternatives will be explained and claimed for this invention, butwith the understanding that such inverses or alternatives are implicit,thus covered by such explanation and claims.

The system 10 for characterizing, encoding, and storing images by shapecontent of such images, as illustrated diagrammatically in FIG. 5, is anexample application of the segmented radial SLM device 50 describedabove and is a part of this invention. In this system 10, any number nof images 12, 14, . . . , n, can be characterized and encoded by theshape content in such images, and such encoded shape information abouteach image can be stored, for example, in database 102 for subsequentsearching, retrieval, and comparison to shape content of other imagesthat is characterized and encoded in the same manner.

The images 12, 14, . . . , n can be in virtually any form, for example,visual images on photographs, films, drawings, graphics, arbitrarypatterns, ordered patterns, or the like. They can also be stored and/orgenerated in or from digital formats or analog formats. Such images canhave content that is meaningful in some manner when viewed by humans, orthey can appear to be meaningless or not capable of being interrupted byhumans but characteristic of some other content, e.g., music, sounds,text, software, and the like. Essentially, any optic pattern of lightenergy intensities that can be manifested or displayed with discernableshape content can be characterized and encoded with this system 10.

A sample image 12, which can be obtained from any source (e.g.,Internet, electronic data base, web site, library, scanner, photograph,film strip, radar image, electronic still or moving video camera, andother sources) is entered into the optical image shape characterizer 10,as will be described in more detail below. Any number n of other sampleimages 14, . . . , n, are shown in FIG. 5 queued for entry in sequenceinto the optical image characterizer 10. Entry of any number n of suchsequential images 12, 14, . . . , n can be done manually or, preferably,in an automated manner, such as a mechanical slide handler, a computerimage generator, a film strip projector, an electronic still or videocamera, a hologram, or the like. The computer 20 in FIG. 5 is apreferred embodiment, but is also intended to be symbolic of anyapparatus or system that is capable of queuing and moving images 12, 14,. . . , n into the image characterizer 10. The example image 12 of anautomobile displayed on the video monitor 22 represents and is symbolicof any image that is placed in a process mode for characterizing andencoding its shape content according to this invention, although itshould be understood that such display of the image being processed isnot an essential feature of this invention. The description that followswill, for the most part, refer only to the first image 12 forconvenience and simplicity, but with the understanding that it couldapply as well to any image 12, 14, . . . , n, etc.

In the embodiment of the system 10 illustrated in FIG. 5, the image 12is inserted into the optical image characterizer 10 in an image plane 19that is perpendicular to the beam of light 27 emanating from the E-SLM26, i.e., perpendicular to the plane of the view in FIG. 5. However, tofacilitate explanation, illustration, and understanding of theinvention, the images 12, 14, . . . , n are also shown in phantom linesin the plane of the view in FIG. 5, i.e., in the plane of the paper.This same convention is also used to project image 12′ produced by theE-SLM 26, the Fourier transform optic pattern 32, the active optic area54, isolated and filtered optic pattern 60, and the detector grid 82from their respective planes perpendicular to the light beams into theplane of the paper for purposes of explanation, illustration, andunderstanding. These components and their functions in the inventionwill be explained in more detail below.

As mentioned above, the image 12 can be entered into the optical imagecharacterizer 10 by the computer 20 and E-SLM 26, as will be describedin more detail below. However, the image 12 will undergo a significanttransformation upon passing through the thin, positive lens 30, alsocalled the Fourier transform (FT) lens. A Fourier transform (FT) of thesample image 12′ rearranges the light energy of the optic pattern ofimage 12′ into a Fourier transform (FT) optic pattern 32, which isunique to the image 12′, even though it is not recognizable as the image12′ to the human eye and brain, and which can be characterized byintensities, i.e., amplitudes, of light energy distributed spatiallyacross the optic pattern 32. The complex amplitude distribution of lightenergy 34 in the optic pattern 32 is the Fourier transform of thecomplex light distribution in the image 12′. Image 12′ is a recreationof the image 12 in monochromatic, preferably coherent, light energy, aswill be described in more detail below, although white light will alsowork. Of course, persons skilled in the art will also recognize that anE-SLM is only one of a number of well-known devices that can create theimage 12′ in monochromatic or white light, and this invention is notlimited to this particular example.

Concentrations of intense light energy in the Fourier transform (FT)optic pattern 32 generally correspond to spatial frequencies of theimage 12′, i.e., how closely together or far apart features in the image12′ change or remain the same. In other words, spatial frequencies arealso manifested by how closely together or far apart light energyintensities across the light beam 27 change or remain the same. Forexample, a shirt with a plaid fabric in an image (not shown), i.e.,having many small squares, would have a higher spatial frequency, i.e.,changes per unit of distance, than a plain, single-color shirt (notshown) in the image. Likewise, portions of an image, such as the bumperand grill parts 35 of the automobile in image 12′, would have a higherspatial frequency than the side panel 36 portion of the automobile image12′, because the bumper and grill parts 35 comprise many small pieceswith various edges, curves, and other intricate changes within a smallspatial distance, whereas the side panel 36 is fairly smooth and uniformover a large spatial distance. Light energy from the finer and sharperdetails of an image (more spatial frequency), such as the more intricatebumper and grill parts 35 of the image 12′, tend to be dispersed fartherradially outward from the optical center or axis 40 in the Fouriertransformed image than light energy from more course or plain details ofan image (less spatial frequency), such as the side panel 36 of theimage 12′. The amplitude of light energy 34 dispersed radially outwardin the Fourier transform optic pattern 32 is related to the light energyof the corresponding portions of the optic pattern of image 12′ fromwhich such light energy emanates, except that such light energy isconcentrated into areas or bands 34 at the plane of the Fouriertransform (FT) optic pattern 32 after they are refracted by the FT lens30, i.e., into bands of intense light energy separated by bands oflittle or no light energy, which result from constructive anddestructive interference of the diffracted light energy. If the highspatial frequency portions of the image 12′, such as the bumper andgrill portion 35, are bright, then the intensity or amplitude of lightenergy from those high spatial frequency portions of the image 12′,which are dispersed by the FT lens 30 to the more radially outward bandsof light energy 34 in the Fourier transform optic pattern 32, will behigher, i.e., brighter. On the other hand, if the high spatial frequencyportions of the optic pattern of image 12′ are dim, then the intensityor amplitude of light energy from those high spatial frequency portionsof the optic pattern of image 12′, which are dispersed by the FT lens 30to the more radially outward bands of light energy 34 in the Fouriertransform optic pattern 32, will be lower, i.e., not so bright.Likewise, if the low spatial frequency portions of the optic pattern ofimage 12′, such as the side panel portion 36, are bright, then theintensity or amplitude of light energy from those low spatial frequencyportions of the optic pattern of image 12′ which are dispersed by the FTlens to the less radially outward bands of light energy 34 in theFourier transform optic pattern 32 (i.e., closer to the optical axis40), will be higher, i.e., brighter. However, if the low spatialfrequency portions of the optic pattern of image 12′ are dim, then theintensity or amplitude of light energy from those low spatial frequencyportions of the optic pattern of image 12′, which are dispersed by theFT lens 30 to the less radially outward bands of light energy 34 in theFourier transform optic pattern 32, will be lower, i.e., not so bright.

In summary, the Fourier transform optic pattern 32 of the lightemanating from the image 12′: (i) is unique to the image 12′; (ii)comprises areas or bands of light energy 34 concentration, which aredispersed radially from the center or optical axis 40, that representspatial frequencies, i.e., fineness of details, in the image 12′; (iii)the intensity or amplitudes of light energy 34 at each spatial frequencyarea or band in the Fourier transform optic pattern 32 corresponds tobrightness or intensity of light energy emanating from the respectivefine or course features of the image 12′; and (iv) such light energy 34in the areas or bands of the Fourier transform optic pattern 32 aredetectable in intensity and in spatial location by this invention.

Since this optical image characterizer 10 of this invention is designedto characterize an image 12 by shapes that comprise the image 12,additional spatial filtering of the Fourier transform light energypattern 32 is used to detect and capture light energy emanating from thefiner or sharper details or parts of such finer or sharper details inthe image 12′, which are aligned linearly in various specific angularorientations. Such spatial filtering can be accomplished in any of anumber of different ways, as will be explained in more detail below, butan exemplary spatial filter arrangement for this function is included ina combination of the segmented radial spatial light modulator device 50with the polarizing beam splitter 70. Essentially, the segmented radialSLM device 50 rotates the plane of polarization of selected portions ofthe Fourier transform optic pattern 32 from p-plane polarization tos-plane polarization, or vice versa, as explained above, and thepolarizing beam splitter 70 separates light energy of those portionsthat is isolated and polarized in one plane from the light energy of therest of the Fourier transform optic pattern 32 that remains polarized inthe other plane so that such light energy of the selected and isolatedportions can be detected separately.

In the example, segmented radial SLM 50 shown in FIGS. 1–4 only theportions of the light energy 34 in the Fourier transform pattern 32 thatalign linearly with selected active optic segments, for example, segment502, 504, 506, and/or 508 (FIG. 3), have the plane of polarizationrotated in the reflected light 61(s) by the segmented radial SLM 50. Inthis example, such selected portions 61(s) of the beam 27(p) represent,i.e., emanated largely from, details or features of the image 12′, suchas straight lines and short segments of curved lines, that alignlinearly with the angular orientation of the respective sectors 500,510, 520, 530, 540, 550, 560, 570, 580, 590, 600, 610, 620, 630, 640,650 in which selected segments are located in the active optic area 54of the segmented radial SLM 50. For example, if one or more of thesegments 502, 504, 506, 508 in sector 500 is selected and activated torotate plane of polarization of light energy reflected from suchsegments(s), the reflected light energy 61(s) will have emanated largelyfrom details or features of the image 12′ that align linearly with thevertical orientation of the sector 500 in which segments 502, 504, 506,508 are positioned. Further, since the light energy 34 from higherspatial frequency content of the image 12′, e.g., closely spaced bumperand grill parts 35, are dispersed farther radially outward in theFourier transform optic pattern 32 than light energy 34 from lowerspatial frequency content, e.g., side panel 36, the light energy inreflected light beam 61(s) will also be characteristic of a confinedrange of such spatial frequency content of image 12′, depending on whichsegment of a sector is selected. For example, activation of outersegment 508 of sector 500 (FIG. 3), which is positioned farther radiallyoutward from the optic axis 40 of the incident beam 27(p) than segment502, will cause the light energy in reflected beam 61(s) to becharacteristic of higher spatial frequency content of verticallyoriented features in image 12′, e.g., vertical edges of bumper and grillparts 35. In contrast, activation of inner segment 502 of sector 500,will cause the light energy in reflected beam 61(s) to be morecharacteristic lower spatial frequency content of vertically orientedfeatures in the image 12′, e.g., the vertical rear edge of the trunk lid37. The result is a filtered pattern 60 of light energy bands 62 thatrepresent or are characteristic of the unique combination of features orlines in the content of image 12′ that corresponds to light energy ofthe FT optic pattern 32 at the radial distance of the selected segment,sometimes called “scale”, and that align linearly with the sector inwhich the selected segment is positioned. Therefore, in addition tobeing able to provide rotational spatial filtering of the FT opticpattern 32 at different angular orientations about the optic axis, thesegments of each sector, such as segments 502, 504, 506, 508 of sector500, provided the additional capability of scalar spatial filtering FToptic pattern 32 at different radial distances from the optic axis.

Of course, segments in different sectors of different angularorientations about the optic axis 40 will align linearly with featuresor lines in the image 12′ that have different angular orientations, aswill be described in more detail below. Thus, the light energy bands 62in the filtered pattern 60 will change, as active optic segments indifferent sectors are selected and activated, to represent differentfeatures, details, edges, or lines in the optical pattern of image 12′at various angular orientations, intricateness or fineness, andbrightness, as will be explained in more detail below. In general,however, the light energy bands 62, if inverse Fourier transformed fromthe FT optic pattern 32 after the above-described spatial filtering 54,will be located in the same spatially-related sites as the features inthe original image 12′ from which such light energy emanated. Forexample, light energy in a band 62 in pattern 60 that originallyemanated from bumper and grill parts 35 in image 12′, after spatialfiltering with the vertical sector of the bumper and grill parts 35 inimage 12′.

The spatially filtered light energy in bands 62 of the filtered pattern60 can be detected by a photodetector 80 at any of the various angularorientations of the activated sectors and fed electronically to acomputer 20 or other microprocessor or computer for processing andencoding. While only one photodetector 80 with an example 16×16 array 82of individual photosensitive energy transducers 84 is illustrated inFIG. 5 and is sufficient for many purposes of this invention, otherdetector arrangements, for example, the two offset detector arraysdescribed in co-pending patent application, Ser. No. 09/536,426, or oneor more larger detector arrays, could also be used.

The computer 20, with input of information about the filtered opticalpatterns 60, i.e., light energy intensity (I) distribution, from thedetector array 82, along with information about the image 12 (e.g.,identification number, source locator, and the like), information aboutthe angular orientation (R) of the sector in which a segment isactivated, and information about the radial distance or scale (S) of theactivated segment relating to spatial frequency, can be programmed toencode the characteristics of the image 12 relating to the shape contentof the image 12. One useful format for encoding such information is bypixel of the filtered image 60, including information regarding x, ycoordinate location of each pixel, Rotation (i.e., angular orientationof the sector in which a segment is activated, thus of the linearfeatures of the image 12 that align with such angular orientation), andIntensity (i.e., amplitude of light energy from the filtered pattern 60that is detected at each pixel at the angular orientation R. Asearchable flag, such as a distortion factor X, can also be provided, asexplained in more detail co-pending patent application, Ser. No.09/536,426 or by the ghost image pre-processing feature of thisinvention, which will be explained in more detail below. Suchcombination of angular orientation or rotation R, light energy intensityI for each pixel, and distortion factor X can be called a “RIXel” forshort. Scale (i.e., spatial frequencies of image 12 content at suchangular orientations) can also be included in such encoding, if desired.When including a scale factor S, the combination can be called a“RIXSel”. Each RIXel or RIXSel can then be associated with someidentifier for the image 12 from which it was derived (e.g., a number,name, or the like), the source location of the image 12 (e.g., InternetURL, data base file, book title, owner of the image 12, and the like),and any other desired information about the image, such as format,resolution, color, texture, content description, search category, or thelike. Some of such other information, such as color, texture, contentdescription, and/or search category, can be information input fromanother data base, from human input, or even from another opticalcharacterizer that automatically characterizes the same image 12 as tocolor, texture, or the like—whatever would be useful for searching,finding, or retrieving image 12 or for comparing image 12 to otherimages.

Some, all, or additional combinations of such information about eachimage 12, 14 . . . , n characterized for shape and encoded, as describedabove, can be sent by the computer 20 to one or more data base(s) 102.Several example data base architectures 104, 106, 108 for storing RIXelor RIXSel information about each image 12, 14, . . . , n are shown inFIG. 5, but many other architectures and combinations of informationcould also be used.

In the optical image characterizer 10 illustrated in FIG. 5, the image12 has to be recreated with monochromatic, preferably coherent, orwhite, light energy, e.g., at image 12′. For example, a monochromaticimage 12′ can be recreated with a spatial light modulator (SLM) 26illuminated with a beam of monochromatic light 24 from a light source23, such as a laser diode or gas diode. This feature of the inventioncould also be implemented with white light, although the resultantFourier transform optic patterns and spatially filtered optic patternswould be more blurred than with monochromatic light. Therefore, whilethis description of the invention will proceed based on monochromatic,preferably coherent, light, it should be understood that white light isa suitable, albeit not a preferred, substitute. The spatial lightmodulator (SLM) 26 can be optically addressable (0-SLM), such as the oneillustrated in co-pending patent application Ser. No. 09/536,426, or itcan be electrically addressable (E-SLM) and driven, for example, by acomputer 20 in FIG. 5 or by a video camera (not shown). As is known bypersons skilled in the art, a spatial light modulator (SLM) can “write”an image into a polarized beam of light 25 by rotating or partiallyrotating the polarization plane of the light on a spatial basis acrossthe beam 25 so that, upon reflection as beam 27, it is eithertransmitted through, or reflected by, the polarization beam splitter116, depending on what is needed to create the image 12′ inmonochromatic light. In an optically addressed SLM (not shown), theimage plane is addressed on a spatial basis by incident light energy ona semiconductor material adjacent the polarization rotating material(usually a liquid crystal material), whereas, in an electricallyaddressable SLM 26, the liquid crystal, polarization rotating materialis addressed electrically on a pixel by pixel basis. The pixel portionsof the polarized light that have the plane of polarization rotated 45degrees as they pass once through the liquid crystal material, whereuponsuch light is reflected and passed back through the liquid crystalagain, where it is rotated another 45 degrees. Thus, the pixels of lightin polarized beam 25 that have their plane of polarization rotated inthe SLM 26 are reflected and emerge from the SLM along the optical path27, which has an optic axis 40 that coincides with the optic axis of theincident beam 25 but in an optic pattern imposed by the E-SLM 26 thatforms an image 12′ and with its plane of polarization rotated 90 degreesfrom the plane of polarization of the incident beam 25. The remainingpixels of light, which do not undergo rotation of the plane ofpolarization, are also reflected, but they can be separated from thosethat have undergone rotation of plane of polarization, as will beexplained below. Various light intensities or brightnesses of the image12 can be recreated in gray scales in image 12′ by partial rotations ofplane of polarization. Persons skilled in the art may also be able tocreate the image 12′ holographically or with other devices or systems,and this invention is not limited by any particular apparatus or methodof creating image 12′.

In the FIG. 5 example embodiment, the coherent light beam 24 from lasersource 23 is passed first through a polarizer 28 to create a polarizedbeam of coherent light 25 with all the light polarized in one plane,such as, for example, but not for limitation, in the s-plane, asindicated by 25(s). The s-polarized beam 25(s) is then passed through aspatial filter 110 comprised essentially of a pin hole 112 and a lens114 to focus the beam 25(s) on the pin hole 112. This spatial filter 110is provided primarily to condition the beam 25(s) to get a good Gaussianwavefront and, if necessary, to limit the power of the beam 25(s). Lens114 a then columnates the light. Of course, the initial beam 25 could bep-polarized, instead of s-polarized to implement this invention withinverses of the example planes of polarization illustrated in FIG. 5 anddescribed herein, which would work just as well.

The beam 25(s) is then passed through a polarizing beam splitter 116,which reflects light polarized in one direction at plane 118 andtransmits light polarized in the orthogonal direction. In this example,the polarizing beam splitter 116 reflects s-polarized light andtransmits p-polarized light, and it is oriented to reflect thes-polarized beam 25(s) toward the electrically addressed spatial lightmodulator (E-SLM) 16. The monochromatic, preferably coherent, light beam25(s) incident on the E-SLM 36 provides the light energy that isutilized to carry the shape content of the image 12′ for furtheranalysis, characterization, and encoding according to the principles ofthis invention in the examples described below.

As mentioned above, there are many ways of “writing” images 12, 14, . .. , n into a light beam, one of which is with an E-SLM 16. In thisexample, computer 20 has the content of image 12 digitized, so thecomputer 20 can transmit digital signals via link 21 to the E-SLM 26 ina manner that addresses and activates certain pixels in the E-SLM 26 to“write” the image 12′ into reflected light beam 27(p), as is understoodby persons skilled in the art. Essentially, the addressed pixels rotatethe plane of polarization by 90 degrees from the s-plane of incidentbeam 25(s) to the p-plane of reflected beam 27(p), or by some lesseramount for gray-scales, in a manner such that the reflected light energywith partially or fully 90-degree polarization plane rotation is in amonochromatic optical pattern of the image 12′. Of course, personsskilled in the art will also understand that the image 12′ could also becreated with an E-SLM that operates in an opposite manner, i.e., theplane of polarization is rotated in reflected light, except where pixelsare activated, in which case the computer 20 would be programmed toactivate pixels according to a negative of the image 12 in order towrite the image 12′ into reflected beam 27. Either way, the emergingbeam 27(p) of coherent light, carrying image 12′, is p-polarized insteadof s-polarized or vice versa. Consequently, in the above example, themonochromatic light beam 27(p), with its light energy distributed in anoptic pattern that forms the monochromatic image 12′, is transmitted bythe polarizing beam splitter 116 to the FT lens 30, instead of beingreflected by it.

The positive Fourier transform (FT) lens 30, as explained above ispositioned in the light beam 27(p) and redistributes the monochromaticlight energy from the image 12′ into its Fourier transform optic pattern32, which occurs at the focal plane of the FT lens 30. Therefore, thesegmented radial SLM 50 of this invention is shown positioned in thefocal plane of the FT lens 30, as indicated by the focal distance F inFIG. 5, and the FT lens 30 is also positioned the same focal distance Ffrom the E-SLM 26, so that the E-SLM 26 is also in a focal plane of thelens 30. As also explained above, the complex amplitude distribution oflight energy 34 in the Fourier transform optic pattern 32 at the focalplane of the FT lens 30 is the Fourier transform of the complexamplitude distribution in the image 12′. The Fourier transform opticpattern 32 has all of the light energy from the image 12′ distributedinto the symmetrical pattern 32 based on the spatial frequencies of theimage 12′, with intensities of the light energy in the various spatialfrequency distributions 34 based on the light energy in thecorresponding portions of the image 12′ where those respective spatialfrequencies occur.

Of course, the Fourier transform optical pattern can also be projectedand captured or spatially filtered according to this invention inlocations other than the focal plane of the lens 30 by appropriateoptical components or systems (not shown), as is well-known by personsskilled in the art. For example, but not for limitation, another lens(not shown) positioned behind the focal plane of the lens 30 can formand project an enlargement of the FT image in a different plane, asexplained in the U.S. Pat. No. 3,771,124, issued to D. McMahon.Therefore, while the example implementation of this invention shown inFIG. 5 illustrates the segmented, radial SLM 50 positioned in the focalplane of the FT lens 30, it could be positioned in any plane where theFourier transform optic pattern 32 occurs.

The Fourier transform optic pattern 32, as mentioned above, issymmetrical from top to bottom and from left to right, so that eachsemicircle of the Fourier transform optic pattern 32 contains exactlythe same distribution and intensity of light energy as its oppositesemicircle. Light energy from lower spatial frequencies in the image 12′are distributed toward the center or optical axis 40 of the Fouriertransform optic pattern 32, while the light energy from higher spatialfrequencies in the image 12′ are distributed farther away from theoptical axis 40 and toward the outer edge of the pattern 32, i.e.,farther radially outward from the optic axis 40. Light energy fromfeatures in the image 12′ that are distributed vertically in the image12′ to create those various spatial frequencies is likewise distributedvertically in the Fourier transform optic pattern 32. At the same time,light energy from features in the image 12′ that are distributedhorizontally in the image 12′ to create those various spatialfrequencies is distributed horizontally in the Fourier transform opticpattern 32. Therefore, in general, light energy from features in theimage 12′ that are distributed in any angular orientation with respectto the optical axis 40 to create the various spatial frequencies in theimage 12′ is also distributed at those same angular orientations in theFourier transform optic pattern 32. Consequently, by detecting onlylight energy distributed at particular angular orientations with respectto the optical axis 40 in the Fourier transform optic pattern 32, suchdetections are characteristic of features or details in the image 12′that are aligned linearly in such particular angular orientations. Theradial distributions of such detected light energy at each such angularorientation indicate the intricateness or sharpness of such linearfeatures or details in the image 12′, i.e., spatial frequency, while theintensities of such detected light energy indicate the brightness ofsuch features or details in the image 12′.

Therefore, a composite of light energy detections at all angularorientations in the Fourier transform optic pattern 32 creates acomposite record of the shapes, i.e., angular orientations,intricateness or sharpness, and brightness, of linear features thatcomprise the image 12′. However, for most practical needs, such as forencoding shape characteristics of images 12, 14, . . . , n for data basestoring, searching, retrieval, comparison and matching to other images,and the like, it is not necessary to record such light energy detectionsfor all angular orientations in the Fourier transform pattern 12′. It isusually sufficient to detect and record such light energy distributionsand intensities for just some of the angular orientations in the Fouriertransform optic pattern 32 to get enough shape characterization to bepractically unique to each image 12, 14, . . . , n for data basestorage, searching, and retrieval of such specific images 12, 14, . . ., n. For purposes of explanation, but not for limitation, use of11.25-degree angular increments is convenient and practical, becausethere are sixteen (16) 11.25-degree increments in 180 degrees ofrotation, which is sufficient characterization for most purposes and hasdata processing and data storage efficiencies, as explained inco-pending U.S. patent application Ser. No. 09/536,426. However, otherdiscrete angular increments could also be used, including constantincrements or varying increments. Of course, varying increments wouldrequire more computer capacity and more complex software to handle thedata processing, storing, and searching functions.

In the preferred embodiment of this invention, the segmented radial SLM50, shown in FIG. 1, with its active optic sectors 500, 510, 520, 530,540, 550, 560, 570, 580, 590, 600, 610, 620, 630, 640, 650 shown in FIG.2, is used to select only light energy from specific angularorientations in the Fourier transform optic pattern 32 for detection atany instant in time or increment of time on the detector array 82. Asexplained above with reference to the sector 500 in FIG. 3, which,except for angular orientation, is typical of all the other sectors 510,520, 530, 540, 550, 560, 570, 580, 590, 600, 610, 620, 630, 640, 650 inFIG. 2, any active optic segment, e.g., segments 502, 504, 506, 508, invertical sector 500, can be addressed via respective electric traces,e.g., traces 503, 505, 507, 509 for sector 500, so that the detectorarray 82 can detect light energy distribution and intensity (I) in theFourier transform optic pattern 32 at any angular orientation (R) of asector 500, 510, 520, 530, 540, 550, 560, 570, 580, 590, 600, 610, 620,630, 640, 650 and at selected radial distances from the optic axis 40.For example, sector 500 is oriented substantially vertical in relationto the optic axis 40. If all of the active optic segments 502, 504, 506,508 of sector 500 are selected and activated simultaneously, virtuallyall of the light energy that is distributed vertically in the Fouriertransform optic pattern 32 will be incident on, and detected by, thephotodetector array 82 (FIG. 5). However, if only one of the activeoptic segments, for example, outer segment 508, is selected andactivated, then only the light energy in the Fourier transform opticpattern 32 that is distributed vertically and the farthest radiallyoutward from the optic axis 40 will be detected by the photodetectorarray 82. Thus, any one, all, or combination of the active opticsegments, e.g., 502, 504, 506, 508, can be activated sequentially orsimultaneously to detect and record various distributions of lightenergy in the Fourier transform optic pattern 32. Also, any one or moresectors 500, 510, 520, 530, 540, 550, 560, 570, 580, 590, 600, 610, 620,630, 640, 650 can be selected and activated sequentially,simultaneously, or in various combinations, depending on the detail orparticular light energy distributions in the FT optic pattern 32 it isdesired to detect.

The preferred, but not essential, shape of the active optic sectors,e.g., sector 500, in the segmented radial SLM 50 is a narrow, elongatedwedge. The width of the wedge will depend on the light energy availableor needed and the optic resolution desired. A wider sector will directmore light energy 34 to the detector 80, but precision of line orfeature resolution of the image 12′ will degrade slightly. A narrowersector will get better line resolution, but with a correspondingincrease in the complexity of the resulting pattern shape generalizationand complexity and a decrease in light energy directed to the detector80. There may also be a practical limitation as to how narrow and closethe wedges can be made with the connecting electric traces in a limitedactive optic area 54 in an economic and efficient manner. Therefore, adesirable balance between these resolution, detectability, and sizeconsiderations may be struck in choosing sector size. Also, forspecialized applications, sectors of different shapes (not shown), suchas ovals, or other shapes could be used to capture shapes other thanlines from the image 12.

The number of active optic segments in a sector, e.g., the four segments502, 504, 506, 508 in sector 500, also has similar constraints. Smallersegments direct less light energy to the detector 80, but may providemore resolution of shape characteristics of the image 12′, whereaslarger segments direct more light to the detector 80, thus are moreeasily detectable, but resolution decreases. For lower resolutionapplications or requirements, the sectors may not even need to bedivided into segments, and this invention includes radial spatial lightmodulators in which each sector 500, 510, 520, 530, 540, 550, 560, 570,580, 590, 600, 610, 620, 630, 640, 650 is not segmented, thus comprisesa single active optic element for each sector. However, the same lowerresolution effect can be achieved in the illustrated embodiment 50 inFIGS. 1–3 by activating all the segments 502, 504, 506, 508 in a sectorsimultaneously, as described above.

In the preferred embodiment 50, each sector, e.g., sector 500, comprisesfour individually addressable, active optic segments, e.g., segments502, 504, 506, 508, as shown in FIG. 3, although any number of segmentsother than four can also be used according to this invention. The lengthof each successive radial outward segment in this example is twice aslong as the next adjacent radially inward segment. Thus, in sector 500,the near inner segment 504 is about twice as long as the inner segment502. Likewise, the near outer segment 506 is about twice as long as thenear inner segment 504, and the outer segment 508 is about twice as longas the near outer segment 506. Expressed another way, if the radiallength of inner segment 502 is L, the radial length of near innersegment 504 is 2L, the radial length of the near outer segment 506 is4L, and the radial length of the outer segment 508 is 8L. The distance dbetween the optic axis 40 and the inner edge 501 of inner segment 502 isabout the same as the length L of inner segment 502, so the diameter ofthe center area 57 is about 2L. These proportional lengths of the activeoptic segments enable the inner segments (e.g., 502) to capture shapefeatures of the image 12′ that have sizes (in spatial frequency) in arange of about 25–50 percent of the size of the image 12′ produced bythe spatial light modulator 26 in FIG. 5, the near inner segments (e.g.,504) to capture shape features of the image 12′ that have sizes in arange of about 12½–25 percent of the size of image 12′, the near outersegments (e.g., 506) to capture shape features of the image 12′ thathave sizes in a range of about 6¼–12½ percent of the size of image 12,and the outer segments (e.g., 508) to capture shape features of theimage 12′ that have sizes in a range of about 3⅛–6¼ percent of the sizeof the image 12′.

To illustrate, suppose the image 12′ is a pattern of a plurality ofparallel vertical lines intersecting a plurality of parallel horizontallines to form a matrix of squares, as illustrated, for example, in FIG.6 a or in FIG. 7 a. If the squares comprising the matrix are quitelarge, such as the squares 702 in FIG. 6 a, so that the vertical lines704, 706, which define the edges of the squares 702, are spaced farapart from each other by a distance equal to about 25–50 percent ofwidth of the whole image 12′, i.e., low spatial frequency, then thelight energy for that vertical shape content will be incident on theinner segment 502 of the vertical sector 500, as illustrated in FIG. 9.In contrast, if the squares of the matrix are quite small, such as thesquares 722 in FIG. 7 a, so that the vertical lines 724, which definethe edges of the squares 722, are spaced closely together, such as by adistance equal to about 3⅛–6¼ percent of the width of the whole image12′, i.e., high spatial frequency, then the light energy for thatvertical shape content will be incident on the outer segment 508 of thevertical sector 500, as illustrated in FIG. 9. It follows, then, thatlight energy for the vertical shape content of a matrix ofintermediately sized squares (not shown) i.e., intermediate or moderatespatial frequency, would be incident on one or both of the intermediatesegments 504, 506 of the vertical section 500.

Also, light energy for the horizontal shape content of such large,small, or intermediate sized matrix square patterns would be incident onthe respective inner, outer, or intermediate positioned segments of thehorizontal sector 540. For example, in the image 12′ of FIG. 6 a withthe large squares 702, where the horizontal lines 706 are spaced apartby a distance equal to 25–50 percent of the width of the image 12′,i.e., low spatial frequency, the light energy for that horizontal shapecontent will be incident on the inner segment 542 of the horizontalsector 540, as illustrated in FIG. 9. In contrast, the example image 12′of small squares 722 in FIG. 7 a, wherein the horizontal lines 726 arespaced apart by a distance equal to 3⅛–6¼ percent of the width of theimage 12′, i.e., high spatial frequency, the light energy in the FTplane 32 for that horizontal shape content will be incident on the outersegment 548 of the horizontal sector 540, as illustrated in FIG. 9.

Further, any features of an image 12′ that have sizes over 50 percent ofthe size of image 12′, which light energy is incident on the center areaportion 41, can either be captured and detected as an indicator ofgeneral brightness of the image 12′ for intensity control or calibrationpurposes or just ignored and not captured or detected at all, becausethere is little, if any, useable shape information or content in thelight energy that comprises that 50 percent of the size of the image12′. Likewise, the approximately 3⅛ percent of the size content of theimage 12′ that is radially outward beyond the outer segments or sectorsis not detected and can be ignored in this preferred configuration. Thecenter 41 can be made optically active to capture light energy incidentthereon, if it is desired to capture and detect such light energy forgeneral brightness indication, intensity control, or calibrationpurposes, as will be understood and within the capabilities of personsskilled in the art, once they understand this invention. For example, ifan image 12′ has a matrix of squares, which are so large that thedistance between the vertical lines, which define the edges of the largesquares, is over 50 percent of the width of the image 12′, there islittle, if any, vertical shape content of practical use, and the lightenergy for that vertical shape content is incident on the center areaportion 41. On the opposite end of the spectrum, if such an image 12′has a matrix of squares, which are so small that the distance betweenthe vertical lines, which define the edges of the small squares, is lessthan about 3⅛ percent of the width of the image 12′, there is alsolittle, if any, vertical shape content of practical use, and the lightenergy for such vertical shape content is dispersed radially outward,beyond the outer segment 508 of sector 500. Of course, otherconfigurations or scale segment sizes and combinations of the segmentedradial SLM 50 could also be made and used within the scope of thisinvention.

The shape content detection according to this invention will bedescribed in more detail below by use of the example automobile image12′ of FIG. 5. However, it is helpful to understand at this point that,when the image 12′ is a matrix of squares, as described above, and whenthe light energy incident on the vertical sector 500 in the Fouriertransform plane 32 is projected back into a spatial domain image, suchspatial domain image will have been filtered to show only the verticallines at the boundaries of the squares. No horizontal lines would appearin such spatial domain, filtered image, because the light energy withthe horizontal shape content would have been substantially blocked orfiltered out of the image. Further, if the squares of the matrix patternare large, such as the squares 702 in FIG. 6 a described above, thevertical lines 704 of such large squares 702 would only be re-formed andvisible in the spatial domain, if the light energy incident on the nearcenter segment 502 of vertical sector 500 is actuated in a manner thatdoes not block such incident light energy in the Fourier transformplane, but, instead, allows it to project back into the spatial domain.In other words, actuation of the inner segment 502 of vertical sector500 would project that incident light energy back into the spatialdomain to re-form the vertical line 704 portions of that large square702 image, as illustrated in FIG. 6 b. At the same time, actuating theouter segment 508 to pass and not block or filter out light would notproject vertical lines to re-form in the spatial domain, because suchlow spatial frequency light energy from a pattern of such large squares702 is not dispersed radially outward enough to be incident on suchouter segment 508. Therefore, when there is a pattern of large squares702 in the image 12′, as illustrated in FIG. 6 a, actuation of anysegment of the vertical sector 500, other than the inner segment 502,would not result in the re-formed spatial image of the vertical lines704 in FIG. 6 b, but would instead result in a blank, i.e., no spatialimage, as illustrated in FIG. 8.

On the other hand, if the image 12′ has a matrix of very small squares722, thus high spatial frequency, as shown in FIG. 7 a and describedabove, then the light energy in the FT plane 32 is dispersed fartherradially outward to be incident on the outer segment 508 and not on theinner segment 502. Therefore, the outer segment 508 of vertical sector500 would have to be actuated to project such light energy of thevertical lines 724 of FIG. 7 a back into the spatial domain to displaythe vertical lines 724, as illustrated in FIG. 7 b. Further, actuationof the inner segment 502 would not project such vertical lines 724 inthe spatial domain, since there would be no light energy incident onsuch inner segment 502 in that case. Similar results for horizontallines 706 of FIG. 6 a and 726 of FIG. 7 a would be obtained from theseveral segments 542, 548 of the horizontal sector 540, as illustratedin FIGS. 6 b and 7 b.

In summary, for an image 12′ comprising a matrix of squares, asdescribed above, actuation of the inner segment 502 of vertical sector500 and getting vertical liens formed in the spatial domain, whileactuation of the outer segment 508 as well as the intermediate segments5604, 506, in the vertical sector 500 projects no vertical lines in thespatial domain, would show that the vertical shape content of the imagehas low spatial frequency characteristic of large squares 702 in FIG. 6a. Similar analysis with the horizontal sector 540 resulting inhorizontal lines in the spatial domain from actuation of the innersegment 542, but not from actuation of the outer or intermediatesegments 548, 546, 544, would show such horizontal lines 706 to also below spatial frequency characteristic of large squares 702.

If analysis of other non-vertical and non-horizontal sectors 510, 520,530, 550, 560, 580, 590, 600, 610, 620, 630, 640, 650 show no lines inthe spatial domain from those angular orientations, then the recordableresults confirm the shape content of the image 12′ to be only a smalleror larger spatial frequency at some or all of those angularorientations, then the recordable results would confirm some shapecomplexity in addition to the matrix of squares in the image 12′. Thus,shape information, including spatial frequency or scale (S), andintensity (I) at each angular orientation or rotation (R) can beacquired with the spatial light modulator 50 in the system of thisinvention.

In summary, for an image 12′ with the large square 702 matrix shown inFIG. 6 a, the low spatial frequency vertical line 704 shape content ofthat image can only be projected from the FT plane 32 back into thespatial domain illustrated in FIG. 6 b by actuation of the inner segment502 of the vertical sector 500 in FIG. 9. Likewise, the low spatialfrequency horizontal line 706 shape content of that large square matriximage can only be projected from the FT plane 32 back into the spatialdomain illustrated in FIG. 6 c by actuation of the inner segment 542 ofhorizontal sector 540. Actuation of any other segment of sectors 500,510, 520, 530, 540, 550, 560, 570, 580, 590, 600, 610, 620, 630, 640 forthat large square, low spatial frequency, image 12′ of FIG. 6 a willresult only in a blank, as illustrated in FIG. 8, because, with thatkind of low spatial frequency image 12′ having only vertical andhorizontal lines, there will be no light energy incident on such othersegments. Actually, in practice, there could be some amount ofspill-over of light energy incident on some of such other segments,since the optical components and even the physical systems, can seldombe perfect. However, in a simple square grid image, such as shown inFIGS. 6 a and 7 a, such spill-over of light energy to adjacent segmentsand/or sectors would not usually be significant. More complex shapecontent in images could very well cause light energy in the FT plane 32to be incident on one or more adjacent segments and/or sectors atdifferent rotational (R) and radial (S) positions, in which case theintensities (I) of light on any such adjacent segments and/or sectorswould become part of the RIXSel information or shape data for such animage.

While the radial configuration of the active optic sectors with orwithout the multiple, active optic segments in each sector in thespatial light modulator 50 is a significant feature of this invention,persons skilled in the art of designing and fabricating spatial lightmodulators can readily understand how such a spatial light modulator 50can be constructed and function, once they become familiar with thefeatures and principles of this invention, and there are many knownmaterials, fabrication techniques, and the like, known to personsskilled in the art that could be used to design, make, and usestate-of-the-art spatial light modulators that are applicable to thespecialized spatial light modulator embodiments of this invention.Therefore, a detailed recitation of such available materials is notnecessary to enable a person skilled in the art to make and use thisinvention. Never-the-less, reference is now made to FIG. 4 incombination with FIGS. 1–3 and 5 to illustrate one example of howselection and activation of any particular active optic segment, forexample, near outer segment 506 and outer segment 508, function toselectively enable detection of light energy from the Fourier transformoptic pattern 32 that is incident on such segments.

As illustrated in FIG. 4, the optic active segments 506, 508, which aretypical of other active optic segments, are part of an integratedcircuit 52, which is mounted on a chip base or platform 56. Theintegrated circuit 52 has a variable birefringent material 180, such asa liquid crystal material, sandwiched between two transparent substrates182, 184, such as high quality glass. The variable birefringent material180 is responsive to a voltage to change its birefringence in the areaof the voltage, which results in rotation of the plane of polarizationof the light that passes through the material 180. The division betweennear outer segment 506 and outer segment 508 is made by a separation ofrespective metal layers 186, 188. An intervening dielectric orelectrical insulation material 185 can be used to maintain electricalseparation of these metal layers 186, 188. As shown by a combination ofFIGS. 3 and 4, electrically conductive trace 507 is connected to themetal layer 186 of near outer segment 506, and trace 509 is connected tothe metal layer 188 of outer segment 508. In fact, the electric traces507, 509 and metal layers 186, 188 can be deposited on the same metaland can be on the back substrate 184 concurrently with their respectivemetal layers 186, 188 during fabrication of the integrated circuit 52,as would be understood and within the capabilities of persons skilled inthe art of designing and fabricating spatial light modulators, once theyare informed of the principles of this invention. Therefore, the metallayers 186, 188 can be addressed individually through their respectiveconnected traces 507, 509 by connecting positive (+) or negative (−)voltages V₁ and V₂, respectively, to traces 507, 509.

A transparent conductive layer 190 deposited on the front substrate 182is connected by another lead 513 to another voltage V₃. Therefore, avoltage can be applied across the portion of the liquid crystal material180 that is sandwiched between the metal layer 186 and the transparentconductive layer 190 by, for example, making V₁ positive and V₃ negativeand vice versa. Likewise, when a voltage can be applied across theportion of the liquid crystal material 180 that is sandwiched betweenthe metal layer 188 and the transparent conductive layer 190 by, forexample, making V₂ positive and V₃ negative and vice versa.

As mentioned above, the function of the respective segments 506, 508 isto rotate the plane of polarization of selective portions of theincident light beam 27(p) so that those portions of the light beam27(p), which carry corresponding portions of the Fourier transform opticpattern 32, can be separated and isolated from the remainder of thelight beam 27(p) for detection by the photodetector array 82 (FIG. 5).As understood by persons skilled in the art, there are a number ofspatial light modulator variations, structures, and materials that canyield the desired functional results, some of which have advantagesand/or disadvantages over others, such as switching speeds, lighttransmission efficiencies, costs, and the like, and many of which wouldbe readily available and satisfactory for use in this invention.Therefore, for purposes of explanation, but not for limitation, thesegmented radially spatial light modulator illustrated in FIG. 4 canhave respective alignment layers 192, 194 deposited on the transparentconductive layer 190 on substrate 182 and on the metal layers 186, 188on substrate 184. These alignment layers 192, 194 are brushed orpolished in a direction desired for boundary layer crystal alignment,depending on the type of liquid crystal material 180 used, as iswell-understood in the art. See, e.g., J. Goodman, “Introduction toFourier Optics, 2^(nd) ed., chapter 7 (The McGraw Hill Companies, Inc.)1996. An antireflective layer 196 can be deposited on the outsidesurface of the glass substrate 182 to maintain optical transmissiveefficiency.

One example system, but certainly not the only one, can use a liquidcrystal material 180 that transmits light 27(p) without affectingpolarization when there is a sufficient voltage across the liquidcrystal material 180 and to act as a ¼-wave retarder when there is novoltage across the liquid crystal material. An untwisted crystalmaterial 180 that is birefringent in its untwisted state can function inthis manner. Thus, for example, when no voltage is applied across theliquid crystal material 180 in segment 508, there is no molecularrotation of the liquid crystal material 180 in outer segment 508, andthe liquid crystal material in outer segment 108, with the properthickness according to the liquid crystal manufacturer's specifications,will function as a ¼-wave plate to convert p-polarized light 27(p)incident on outer segment 508 to circular polarization as the lightpasses through the untwisted liquid crystal material 180. Upon reachingthe metal layer 188, which is reflective, the light is reflected andpasses back through the liquid crystal material to undergo another¼-wave retardation to convert the circular polarization to linearpolarization, but in the s-plane, which is orthogonal to the p-plane.The reflected light 61(s), therefore, has its plane of polarizationeffectively rotated by 90 degrees in relation to the incident light27(p).

Meanwhile, if there is a sufficient voltage on, for example, the nearouter segment 506, to rotate the long axes of the liquid crystalmolecules into alignment with the direction of propagation of theincident light waves 27(p), thereby eliminating the birefringence of theliquid crystal material 180, then there is no change of the linearpolarization of the light on either its first pass through the liquidcrystal material 180 or on its second pass through the liquid crystalmaterial after being reflected by metal layer 186. Consequently, underthis condition with a voltage applied across the liquid material 180 innear outer segment 506, the reflected light 61(p) is still polarized inthe p-plane, i.e., the same plane as the incident light 27(p).

Many liquid crystal materials require an average DC voltage bias ofzero, which can be provided by driving the voltage V₃ with a square wavefunction of alternating positive and negative voltages for equal times.Therefore, for no voltage across the liquid crystal material 180, theother voltages V₁, V₂, etc., can be driven in phase with equal voltagesas V₃. However, to apply a voltage across the liquid crystal material180 adjacent a particular metal layer 186, 188, etc., to activate thatparticular segment 506, 508, etc., as described above, the respectivevoltage V₁ or V₂, etc., can be driven out of phase with V₃. If thefrequency of the square wave function is coordinated with the switchingspeed of the liquid crystal material 180, one-half cycle out of phasefor a voltage V₁, V₂, etc., will be enough to activate the liquidcrystal material 180 to rotate the plane of polarization of the light asdescribed above.

As mentioned above, other alternate arrangements and known liquidcrystal materials can reverse the results from an applied voltage. Forexample, a twisted liquid crystal material 180 may be used to rotateplane of polarization under a voltage and to not affect plane ofpolarization when there is no voltage.

Referring again primarily to FIG. 5 with continuing secondary referenceto FIG. 4, the light energy in the beam 27′(p), which passes through thepolarizing beam splitter 116 and 70 without reflection by planes 116 and72, is focused as the Fourier transform optic pattern 32 on thesegmented radial SLM 50. Selected active optic segments, for example,segments 502, 504, 506, 508, in the segmented radial SLM, can rotate theplane of polarization of portions of the incident light beam 27(p), asdescribed above, in order to separate and isolate light energy fromselected portions of the FT optic pattern 32 for detection byphotodetector 80. The computer 20 can be programmed to provide signalsvia link 198 to the segmented radial SLM 50 to select and coordinateactivation of particular segments, for example, segments 502, 504, 506,508, with displays of particular images 12, 14, . . . , n. The computer20 can also be programmed to coordinate laser source 23 via a link 29 toproduce the required light energy 24, when the selected segment of thesegmented radial SLM 50 is activated.

The reflected light 61(s) from the segmented radial SLM 50, e.g., lightpolarized in the s-plane reflected from an activated segment, asexplained above, does not pass back through the polarizing beam splitter70 along with p-polarized reflected light. Instead, the s-polarizedreflected light 61(s) is reflected by the plane 72 in the polarizingbeam splitter 70 to the detector 80 in the spatial domain. The lens 78magnifies and focuses the isolated beam 61(s) in a desired size in thespatial domain on the detector array 82 of photodetector 80.

The photodetector array 82, as mentioned above, can be a 16×16 array ofindividual light sensors 84, such as charge coupled devices (CCDs), asshown in FIG. 5, or any of a variety of other sizes and configurations.The x, y coordinates of individual sensors 84 in the array 82 thatdetect light 61(s) can be communicated, along with light intensity (I)information, to the computer 20 or other controller or recording devicevia a link 86, where it can be associated with information bout theimage 12, 14, . . . , n and the angular orientation (R) and/or radialposition (S) of the activated segment(s) in the segmented radial SLM 50that provided the beam 61(s) to the detector 80.

The spatial filtering process described above and its characterizationof the image 12 by shape content is illustrated in more detail in FIGS.10 a–c, 11 a–c, 12 a–c, 13 a–c, and 14 a–c. With reference first to FIG.10 a, the active optic area 54 from FIGS. 1 and 2 is shown in FIG. 10 awith the example sectors 500, 510, 520, 530, 540, 550, 560, 570, 580,590, 600, 610, 620, 630, 640, 650, but, to avoid unnecessary clutter,without the electric traces that were described above and shown in FIGS.1–3. As mentioned above, the sectors can be any desired width or anydesired angular orientation, but a convenient, efficient, and effectiveconfiguration is to provide sectors of 11.25°. For example, a circle of360° divides into 32 sectors of 11.25° each, and a semicircle of 180°divides into sixteen sectors of 11.25° each. Further, as mentionedabove, the light energy distribution in any semicircle of a Fouriertransform optic pattern 32 is symmetric with its opposite semicircle.Therefore, in accordance with this symmetry principle, detection of thelight energy pattern in one semicircle of the FT optic pattern 32, forexample, in the semicircle extending from 0° to 180°, provides effectiveinformation for the entire image 12′, and detection of the light energypattern in the opposite semicircle extending from 180° to 360° providesthe same information. Consequently, to alleviate clutter and betteraccommodate the electric traces (shown in FIGS. 1–3, some of sectors canbe positioned in one semi-circle of the optic area 54 with interveningspaces to accommodate the electric traces (shown in FIGS. 1–3), whileothers of the sectors can be positioned in the opposite semicircle ofthe optic area 54 diametrically opposite to the intervening spaces. Forexample, when the circle is divided into 32 sectors of 11.25° each, only16 of those sectors, such as sectors 500, 510, 520, 530, 540, 550, 560,570, 580, 590, 600, 610, 620, 630, 640, 650 have to be optically activeto detect all of the shape content in the light energy incident on thearea 54. All 16 of such optically active sectors could be positioned inone semicircle of the area 54, or, as explained above, it is moreconvenient and less cluttered to position some of the optically activesectors in one semicircle with intervening spaces and others in theopposite semicircle diametrically opposite to the intervening spaces. Inthe example of FIG. 10 a, any eight of the sectors, e.g., sectors 640,650, 500, 510, 520, 530, 540, 550, separated by non-active areas 641,651, 501, 511, 521, 531, 541, are positioned in one semicircle of thearea 54, while the remaining eight of the sectors 560, 570, 580, 590,600, 610, 620, 630, also separated by non-active areas 561, 571, 581,591, 601, 611, 621, can be positioned in the opposite semicircle, asshown in FIG. 10 a. When each of the 16 active optic sectors 500, 510,520, 530, 540, 550, 560, 570, 580, 590, 600, 610, 620, 630, 640, 650 inthis arrangement is positioned diametrically opposite a non-active area,the symmetry of the FT optic pattern 32 (FIG. 5) effectively allows allof the shape content in the light energy distribution in FT opticpattern 32 to be detected with these sectors—bit including, of course,the light energy incident on the center area portion 41 or that isdispersed radially outward beyond the outer segments, which has little,if any, significant shape content, as explained above.

This principle also facilitates design and fabrication of an effectivesegmented radial SLM 50, because, for every active optic sector, therecan be an adjacent inactive sector or area available for placement ofelectrically conductive traces to the segments, as shown by referenceback to FIGS. 2 and 3. For example, the inactive area 651 between activeoptic segments 500 and 650 accommodates placement of traces 503, 505,and 507 (shown in FIG. 3) to respective segments 502, 504, 506 of activeoptic sector 500. To provide active optic sectors to detect light energyincident on the non-active areas, for example, the non-active area 501in FIG. 10 a between active optic sectors 500, 510, the above-describedsymmetry principle is applied by providing an active optic sector 590 ina position diametrically opposite the said non-active area 501.Therefore, detection of light energy detected in the active optic sector590 is effectively detecting light energy incident on the non-activearea 501 between sectors 500, 510. In order to have an active opticsector positioned diametrically opposite a non-active area, two of theactive optic sectors, e.g., sectors 550, 560 are positioned adjacenteach other without any significant intervening non-active area, so thediametrically opposite non-active area 631 is twice as big as othernon-active areas. Therefore, according to the above-described symmetryprinciple, substantially all shape content in the light energy 34 of FToptic pattern 32 (FIG. 5) is detectable by the sixteen 11.25° activeoptic sectors 500, 510, 520, 530, 540, 550, 560, 570, 580, 590, 600,610,620, 630, 640, 650.

Returning now to FIG. 10 a, vertical angular orientation is arbitrarilydesignated as 0°, so horizontal angular orientation is at 90°. Eachactive optic sector 500, 510, 520, 530, 540, 550, 560, 570, 580, 590,600, 610, 620, 630, 640, 650 is about 11.25°. Active optic sectors fromsector 640 clockwise to sector 550 are each separated by respectivenon-active areas 641, 651, 501, 511, 521,531, 541 of 11.25°. Therefore,each active optic sector from sector 560 clockwise to sector 630 ispositioned diametrically opposite a respective non-active area 561, 571,581, 591, 601, 611, 621. Consequently, substantially all the shapecontent in the light energy distribution in the FT optic pattern 32(FIG. 4) incident on the active area 54 can be detected in 11.25°intervals by the 11.25° sectors 500, 510, 520, 503, 504, 550, 560, 570,580, 590, 600, 610, 620, 630, 640, 650 positioned as described above.

For example, shape content in the light energy characteristic of thatincident on both the vertical 11.25° sector 500 centered at 0° as wellas on the non-active area 581 centered at 180° can be detected byeffectively activating the active optical segments 502, 504, 506, 508 ofsector 500. Shape content in the light energy characteristic of thatincident on the 11.25° sector 590 centered at 191.25° as well as on thenon-active area 501 centered at 11.25° can be detected effectively byactivating the active optic segments of sector 590, because the activeoptic sector 590 is centered diametrically opposite the non-active areaof 11.25°. Shape content in the light energy characteristic of thatincident on either the 11.25° sector 510 centered at 22.5° or thenon-active area 591 centered at 202.5° can be detected by activating theactive optic segments of sector 510. Shape content in the light energycharacteristic of that incident on either the 11.25° non-active areacentered at 33.75° or active sector 600 centered at 213.75° can bedetected by activating the active optic segments of sector 600, which iscentered diametrically opposite 33.75° at 213.75°. Shape content in thelight energy characteristic of that incident on either the 11.25° sector520 centered at 45° or non-active area 601 centered at 225° can bedetected by activating the active optic segments of sector 520. Shapecontent in the light energy characteristic of that incident on eitherthe 11.25° non-active area 521 centered at 56.25° or the active sector610 centered at 236.25° can be detected by activating the active opticsegments of sector 610, which is centered diametrically opposite 56.25°at 256.25°. Shape content in the light energy characteristic of thatincident on either the 11.25° sector 530 centered at 67.5° or thenon-active area 611 centered at 247.5° can be detected by activating theactive optic segments of sector 530. Shape content in the light energycharacteristic of that incident on either the 11.25° non-active area 531centered at 78.75° or active sector 620 centered at 258.75° can bedetected by activating the active optic segments of sector 620, which iscentered diametrically opposite 78.75° at 258.75°. Shape content in thelight energy characteristic of that incident on either the 11.25° sector540 centered at 90° or non-active area 621 centered at 270° can bedetected by activating the active optic segments of sector 540. Shapecontent in the light energy characteristic of that incident on eitherthe 11.25° non-active area 541 centered at 101.25° or the active sector630 centered at 281.25° can be detected by activating the active opticsegments of sector 630, which is centered diametrically opposite 101.25°at 281.25°. Shape content in the light energy characteristic of thatincident on either the 11.25° sector 550 centered at 112.5° thediametrically opposite portion of non-active area 631 that is centeredat 292.5° can be detected by activating the active optic segments ofsector 550. Shape content in the light energy characteristic of thatincident on the 11.25° sector 560 centered at 123.75°. The diametricallyopposite portion of non-active area 631 that is centered at 303.75° canbe detected by activating the active optic segments of sector 560. Shapecontent in the light energy characteristic of that incident on the11.25° non-active area 561 centered at 135° or active sector 640centered at 315° can be detected by activating the active optic segmentsof sector 640, which is centered diametrically opposite 135° at 315°.Shape content in the light energy characteristic of that incident on the11.25° sector 570 centered at 146.25° or non-active area 641 centered at326.25° can be detected by activating the active optic segments ofsector 570. Shape content in the light energy characteristic of thatincident on the 11.25° non-active area 571 centered at 157.5° or activesector 650 centered at 337.5° can be detected by activating the activeoptic segments of sector 650, which is centered diametrically opposite157.5° at 337.5°. Finally, shape content in the light energycharacteristic of that incident on the 11.25° sectors 580 centered at168.75° or non-active area 651 centered at 348.75° can be detected byactivating the active optic segments of sector 580.

While it would be unnecessarily cumbersome to illustrate and describethe shape detecting and characterizing functionality of all the activeoptic segments of all the sectors 500, 510, 520, 530, 540, 550, 5.60,570, 580, 590, 600, 610, 620, 630, 640, 650, it may be helpful for anunderstanding of the invention to illustrate and describe thefunctionality and results of activating several representative examplesof the active optic segments in the active optic area 54. Therefore,FIG. 10 a illustrates activation of the outer segment 508 of the activeoptic sector 500 by depicting bands of light energy 34 from the FT opticpattern 32 that are incident on and reflected by the outer segment 508.These bands of light energy 34, which are dispersed fartherest radiallyoutward in the vertical direction in the FT optic pattern 32, emanatedoriginally from, and correspond to, substantially vertically orientedlines, edges, features, or details in the image 12′ that have a higherspatial frequency, such as the substantially vertical lines of thebumper and grill parts 35 in FIG. 10 b. As explained above, the lightenergy 34 from the more intricate or closely spaced vertical parts orlines 66 (i.e., higher spatial frequency), such as those in the frontbumper and grill portion 35 of the automobile in image 12′, aredispersed farther radially outward from the optical center or axis 40,thus detectable by activating outer segments 506, 508 of vertical sector500, while the light energy 34 from the less intricate, more isolatedand semi-isolated or farther spaced apart vertical parts, edges, orlines (i.e., lower spatial frequency), such as the substantiallyvertical parts or lines 66′ in the trunk and rear bumper portions of theimage 12′ in FIG. 10 b, are dispersed not so far radially from theoptical center or axis 40 and would be more detectable by inner segments502, 504. The intensity of the light energy 34 in those respectivedispersion bands, as explained above, depends on the brightness of thecorresponding respective vertical features 35, 66, 66′ in the image 12′.Again, the central portion 41 of the active optic area 54 can beignored, if desired, because the light energy 54 in and near the centeror axis 40 of the Fourier transform 32 (FIG. 5) emanates from featuresin image 12′ with very low or virtually no spatial frequencies, such asthe overall brightness of the image, which do very little, if anything,to define shapes. On the other hand, as also explained above, the centerportion 41 can be fabricated as an active optic component to capture andreflect the light energy incident on the center portion 41 to thedetector 80 as a measure of overall brightness, which may be useful incalibrating, adjusting brightness of the source light 25(s) (FIG. 5),calibrating intensity (I) measurements of sensors 84 in detector 80, andthe like.

The light energy bands 34, when reflected by the activated outer segment508, are filtered through the polarizing beam splitter 70 and projectedin the filtered optic pattern 60, which is comprised primary of verticallines or bands 62 of light energy illustrated diagrammatically in FIG. 6c, to the photodetector 80 (FIG. 5). As discussed above, the lightenergy in the filtered optic pattern 60 is detected by the light sensors84 in detector array 82. The intensity (I) of light energy on eachsensor 84 is recorded along with the sensor (pixel) location, preferablyby x-y coordinates, and the angular orientation (R) of the sector 500.The radial position or scale (S) of the activated segment 508(indicative of spatial frequency, as described above) is also recorded,for example, as RIXSel values described above. These values can bestored in a database 102 in association with information about thecharacterized image 12, such as image identification (ID), sourcelocation (URL, database address, etc.) of the image 12, digital format,resolution, colors, texture, shape, subject matter category, and thelike.

To illustrate further, the near inner segment 504 of active optic sector500 is shown in FIG. 11 a as being selected to rotate plane ofpolarization of selected portions of the light energy bands 34 from theFT optic pattern 32 for isolation by the polarizing beam splitter 70 andthen detection by the photodetector 80. This near inner segment 504 isalso in the vertically oriented sector 500, but it is positioned orscaled radially closer to the optic axis 40 than the outer segment 508,which was activated in the previous example. Therefore, this near innersegment 504, when activated, captures light energy 34 in the FT opticpattern 32 that also corresponds to vertical lines, edges, etc., of theimage 12′, but to such lines, edges, etc., of lesser spatial frequencythan those selected by the outer segment 508. For example, instead ofthe closely spaced, vertically oriented bumper and grill parts 35, thelight energy 34 from the FT optic pattern 32 selected by the near innersegment 504 may be more characteristic of the more spatiallysemi-isolated, vertical edge 66′ of the trunk lid and other verticallines and edges 66 of similar semi-isolation in the automobile image 12′in FIG. 10 b. Therefore, the light energy bands 62 in the resultingfiltered beam 61(s), as shown in optic pattern 60 in FIG. 12 c, arecharacteristic of such vertical shape content 66, 66′ of lower spatialfrequency in the image 12′.

Another example angular orientation of light energy 34 from the FT opticpattern 32 is illustrated by FIGS. 12 a–c. The near outer segment 526 inthis example is activated to capture light from lines, edges, orfeatures extending radially at an angular orientation of 45° fromvertical. Such light energy 34 is characteristic of lines, edges, orfeatures in the image 12′ that extend at about 45° and that have somespatial frequency, i.e., are not isolated, such as, perhaps, the windowpost and roof support 67 in FIG. 8 b. Such 45° oriented lines in theimage 12′ with even less spatial frequency, i.e., even more isolated,for example, the portions of the fender and hood edges 67′, might becaptured more by the near inner segment 524 or inner segment 522,although it is possible that some of such light energy could also becaptured by near outer segment 506. The reflected and filtered beam61(s) with the optical pattern 60 for these 45° angular oriented shapecontents have bands 62 of the light energy oriented at about 45°, asillustrated diagrammatically in FIG. 8 c. Such light energy bands 62 aredetected by sensors 84 for photodetector 80 (FIG. 5) and are recordedand stored as characteristic of the spatial frequency of 45°-orientedshape content of the image 12′.

Capture and detection of horizontal portions of lines, edges, andfeatures 68, 68′ of the image 12′ of respective spatial frequencies, ifpresent in the image 12′, is accomplished by activation of one or moresegments 542, 544, 546, 548 of horizontal sector 540, which is oriented90° from the vertical 0°. The portion of the light energy 34 that isreflected by each activated segments 542, 544, 546, 548 of thehorizontal sector 540 is characteristic of all of the substantiallyhorizontal features, parts, and lines 68 of the respective spatialfrequencies in the image 12′ that correspond to the light energy, ifany, that is incident on those segments in the FT plane 32, as shown inFIG. 13 b. Some curved features, parts, or lines in the image 12′ haveportions or line segments 68′ that are also substantially horizontal, sothose horizontal portions or line segments 68′ also contribute to thelight energy 34 that gets reflected by the horizontal sector 540 in FIG.13 a. The bands 62 of light energy in the filtered pattern 60, shown inFIG. 13 c, resulting from the horizontal orientation of an activatedsegments 542, 544, 546, 548 in FIG. 13 a, are also orientedsubstantially horizontal and are indicative of some or all of the shapecharacteristics 68, 68′ of image 12′ that are oriented substantiallyhorizontal. Again, the inner segments 542, 544 are activated to detectlight energy bands 34 from the FT optic pattern 32 that are dispersedcloser to the optic axis 40, thus are characteristic of lower spatialfrequency, horizontal shape content of the image 12′, while higherspatial frequency, horizontal shape content can be detected byactivating the outer segments 546, 548 of the horizontal sector 540.Thus, detection of the light energy bands 62 in FIG. 9 c by detectorarray 82 (FIG. 5) facilitates encoding and recording of the horizontalshape characteristics of the image 12′, as was described above.

One more example activated segment 598 in sector 590, is illustrated inFIG. 14 a to describe the symmetric light energy detection featuredescribed above. As explained above, the light energy bands 34 of the FToptic pattern 32 that are incident on the non-active area between theactive optic sectors 500, 510 are symmetric with the diametricallyopposite light energy bands 34, which are incident on the active opticsegments 529, 594, 569, 598 in sector 590. Therefore, activation of asegment, for example, outer segment 598, as illustrated in FIG. 14 a,will enable effective detection of the same shape content as is in thediametrically opposite, equivalent light energy 34, which is incidentbetween the segments 508, 518 of respective sectors 500, 510. Likewise,activation of any other segment 592, 594, 596 enables effectivedetection of shape content in the other diametrically opposite portionsof light energy that is incident in the non-active area 501 betweenactive sectors 500 and 510. Therefore, detecting light energy 34incident on the sector 590, which is centered at 191.25° in the exampleof FIG. 14 a, is the equivalent of detecting light energy 34 that isincident on the non-active area 501 centered at 11.25°. The oppositealso holds, i.e., detection of light energy 34 incident on the verticalsector 500, as illustrated in FIGS. 6 a and 7 a and described above, isthe equivalent to detecting light energy from the FT optic pattern 32that is incident on the non-active area 581 between active sectors 580and 590.

Referring again to FIGS. 14 a–c, the light energy 34 detected in thesector 590 corresponds to shape content 69, such as lines, edges,portions of curves, and the like in the image 12′ that are orientedsubstantially at about 191.25°, which, being symmetrical, can also beexpressed as oriented at about 11.25°. The light energy bands 62 in thereflected and filtered optic pattern 60 also have that same angularorientation, which is characteristic of the linear shape content of theimage 12′ that has that angular orientation and that has higher spatialfrequency if reflected by outer segments 596, 598 or lower spatialfrequency if reflected by inner segments 592, 594. the optic patterns 60resulting from such various reflected portions of the FT optic pattern32 are detected by the sensors 84 in detector array 82 for recording andstorage, as described above.

It should be clear by now that any particular angular orientation R ofsegments of sectors in the active optic area 54 will allow detection ofall the shape characteristics of image 12′ that have substantially thatsame angular orientation R. It should also be clear that radial outwardspacing or scale (S) of the segments relates to spatial frequency ofsuch shape characteristics. Thus, all of the shape characteristics ofthe image 12′ can be detected by detecting the bands 62 of therespective filtered patterns 60 with the segments at all angularorientations. However, as mentioned above, it is sufficient for mostpurposes to detect some, preferably most, but not necessarily all, ofthe shape characteristics of the image 12′ by choosing to detect thelight energy bands 34 of filtered patterns 60 at certain selectedincrements of or angular orientation or rotation R. Obviously, thebigger the increments of angular orientation of the sectors where lightenergy bands 34 are detected, the less precise the detected shapecharacteristics or contents of the image 12′ will be. On the other hand,the smaller the increments of angular orientation, the more data thatwill have to be processed. Therefore, when selecting the angularincrements of sectors at which light energy bands 34 will be detectedand recorded, it may be desirable to strike some balance betweenpreciseness of shape characteristics needed or wanted and the speed andefficiency of data processing and storage required to handle suchpreciseness. For example, but not for limitation, it is believed thatdetection and recording of the shape characteristics at angularincrements of in a range of about 5 to 20 degrees, preferably about11.25-degrees, will be adequate for most purposes. Also, the angulararea of detection can be varied. For example, even if active opticsectors are oriented to detect shape characteristics at angularincrements of 11.25°, the active optic areas could be narrow, such as ina range of 3° to 8°, more or less, which would filter out some of theoptic energy from the FT optic pattern 32 between the sectors. However,such loss of light energy from non-active areas between sectors or otherradially extending sensors, as described elsewhere in thisspecification, may not be detrimental to shape characterization by thisinvention, depending on specific applications of the technology toparticular problems or goals.

Instead of the radially extending, wedge-shaped active optic sectors andsegments of sectors described above, an alternate configuration can becomprised of radially extending, rectangular-shaped active opticmodulators as illustrated diagrammatically in FIG. 15. Theserectangular-shaped modulators 500′, 510′, 520′, 530′, 540′, 550′, 560′,570′, 580′, 590′, 600′, 610′, 620′, 630′, 640′, 650′ can be at the sameor different angular orientations as the wedge-shaped sectors describedabove, and each angular orientation can comprise several rectangular,active optic segments, such as segments 502′, 504′, 506′, 508′ of themodulator 500′. This arrangement does not capture as much of the lightenergy of an incident FT optic pattern 32 (FIG. 5) as the wedge-shapedsegments and sectors described above, but shape resolution may begreater.

Another, albeit less efficient embodiment, is illustrated in FIG. 16,where the desired sectors and segments, which are shown in phantomlines, can be formed by activating selected groups of light modulatorelements 732 in a pixel array 730 type of spatial light modulatorsimultaneously. For example, a virtual outer segment 508″ of a verticalsector 500″ can be activated by activating simultaneously a segmentgroup 508″ of the light modulator pixel elements 602. While there areversatility advantages to this type of implementation, such advantagesmay be outweighed by the complexity and cost as compared to the simplerconfigurations described above.

While the reflective spatial light modulator structure described abovein connection with the cross-sectional view of FIG. 4 may be applicableto all of the segmented radial SLM 50 configurations described above, analternative, transmissive, spatial light modulator structure 50′illustrated in FIG. 17 could also be used with each of theconfigurations. In this embodiment 50′, the metal reflective layers 186,188 are replaced by transparent conducting layers 186′, 188′, such asindium tin oxide (ITO) or any of a number of other well-knowntransparent conducting materials. Therefore, incident 27(p) may or maynot have its plane of polarization rotated, depending on whether avoltage V is applied to either layer 186′ or 188′, but, instead of beingreflected, the light is transmitted through the device 50′ to emerge aslight energy 61(s) or 61(p), as indicated in FIG. 17. This device ismounted around its periphery in a base 56, so the base 56 does notinterfere with the light 61(s) and 61(p) propagation. A different liquidcrystal material 180′ and/or a different thickness of liquid crystalmaterial than the liquid crystal material 180 for the FIG. 4 embodimentwould be required, since the light passes only once through the liquidcrystal material 180′. However, such materials and their applicationsare readily available and well-known in the art and can be implementedby persons skilled in the art, once the understand the principles ofthis invention. Also, since the light 61(s) is transmitted rather thanreflected, the polarizing beam splitter 70 (FIG. 5) would also have tobe positioned behind the segmented radial SLM 50′ of FIG. 17 instead ofin front of it. However, this modification could also be implementedquite easily by persons skilled in the art, thus is not shown explicitlyin FIG. 5.

In the description above of the preferred implementation of thisinvention, the shape content of a desired angular orientation (R) andscale (S) of an image is captured by masking or blocking all other lightin the FT plane 32 from reaching the detector 80 so that only the lightenergy from that angular orientation (R) and scale segment of the FTplane 32 gets projected back into the spatial domain for detection.However, persons skilled in the art will recognize that this inventioncan also be practiced in the negative. In other words, instead ofactuating the one or several segments and/or sectors to get shapecontent relevant to the angular orientation or rotation (R) and/orradial distance (S) of particular sectors and/or segments, as describedabove, it would also be feasible to actuate all of the other sectors andsegments in the active optic area 54 and not actuate the specific sectorand/or segments in order to get a negative or inverse of the shapecontent of the image. This procedure can be repeated for all of thedesired angular (R) and/or scalar (S) sectors and segments so that thecomposite of information regarding light energy distribution collectedand recorded represents a negative or inverse of all of the shapecontent of an image 12′.

For example, referring back to FIGS. 6 a–c, the negative or inverse ofthe vertical shape content of FIG. 6 a in the spatial domain afteroptical filtering in the FT plane 32 by the segmented radial SLM 50(FIG. 5) would appear as the horizontal lines 706, similar to the waythey appear in FIG. 6 c, with the vertical lines 704 filtered out of thespatial image by the non-actuated inner segment 502 of vertical sector500. If there was more shape content than the squares in FIG. 6 a, thensuch additional shape content would also show in the negative spatialimages, as long as it would not be in the vertical orientation and inthe spatial frequency range that is filtered out of the image by theinner segment 502. Likewise, the negative or inverse of the horizontalshape content of FIG. 6 a in the spatial domain after optical filteringin the FT plane 32 by the segmented radial SLM 50 would appear as thevertical lines 704, similar to the way they appear in FIG. 6 b, with thehorizontal lines filtered out of the spatial image.

To explain further, a negative of the spatially filtered image 60 of theautomobile illustrated in FIG. 10 b would show all of the shape contentof the automobile, except the vertical lines 62′ shown in FIG. 10 c. Thesame differences would apply to negatives for FIGS. 11 c, 12 c, 13 c,and 14 c.

Again, as with the positive spatial images of the shape content, suchnegative or inverse spatial images can be detected at 80 (FIG. 5) bypixels at x-y coordinate locations and intensity (I) and processed forstorage with angular orientation (R) and, if desired, radial scale (S)of the non-actuated sectors and segments, as described above. Also,negative filtered image data can be converted to positive filtered imagedata and vice versa, as would be understood by persons skilled in theart.

The accuracy, versatility, and efficiency of shape characterizing,processing, storing, searching, comparing, and matching images accordingto this invention can be enhanced by some pre-processing of the images12, 14, . . . , n when creating the optical patterns for the images 12′,14′, . . . , n′ at the SLM 26 in FIG. 5. One particularly beneficialmethod of such pre-processing is “ghosting” the image to allow morelight energy into the optic pattern 12′, thus also allowing more lightenergy into the FT optic pattern 32.

With reference now to FIGS. 18 a–c, the ghosting process of thisinvention is illustrated first with an image content of a simple dot,such as a typed period 800, which is illustrated as greatly enlarged inFIG. 18 a. The computer 20 (FIG. 5) or other microprocessor can firstcreate an image of only the edge 802 of the dot 800, as illustrated inFIG. 14 b. Myriad edge-finding software programs are availablecommercially to perform such edge-finding tasks, such as Labview IMAQ™available from National Instrument Corporation, of 11500 MopacExpressway, Austin, Tex. More complex images 12, 14, . . . , n would, ofcourse, have more edge content. Elimination of non-edge content of theimages 12, 14, . . . , n does not degrade the shape characterizingfunction or performance of this invention, because the edges define theshape characteristics and produce the detectable FT optic patterns 32.As was explained above, plain, uniform, unchanging portions of images,such as the side panel 36 of the automobile in image 12′ or the clearblue sky in a landscape picture 14 do not contribute significantdetectable shape content to such images. As also explained above, lightenergy from such plain, uniform, unchanging portions of images tends tofocus on or very near the optic axis 40 in Fourier transform opticpatterns 32, thus would be incident primarily on the center section 41of the segmented radial SLM 50 (see FIG. 2) and is either not detectedat all or detected only to determine background brightness of the image,as explained above.

After the image 800 is converted to an optic pattern of the edge content802 of the image 800, as illustrated in FIG. 18 b, it is ghosted bycreating a plurality of ghost images of the edge content 802. Forexample, as illustrated in FIG. 18 c, a plurality of ghost images 802_(A), 802 _(B), 802 _(C) are created and added to the optic pattern ofthe edge image 802. In this example, a first set of eight ghost images802 _(A) is added a first radial distance r₁ outward from the originaledge image 802 at 45° angular increments. A second set of eight moreghost images 802 _(B) are added another radial distance r₂ outward fromthe ghost images 802 _(A) and at 45° angular increments, and a third setof eight ghost images 802 _(C) are added another radial distance r₃outward and at 45° increments. Each of the ghost images 802 _(A), 802_(B), 802 _(C) have the same shape and are of the same size as theoriginal edge image 802. Therefore, while there is more light energy andmore spatial frequency in the ghosted image 802′ of FIG. 18 c than inthe edge image 802 of FIG. 18 b, there is no new shape content.Consequently, there will be both a wider radial dispersement andincreased intensity of light energy 34 in the FT optic pattern 32 (FIG.5), which can be detected with the segmented radial SLM 50 and detector80. The higher intensity light energy makes it easier for the sensors 84in detector 80 to detect the light energy diverted by the segmentedradial SLM 50 to the detector 80.

The wider radial dispersion of light energy in FT optic pattern 32 dueto the higher spatial frequency content in the ghosted image 802′ ofFIG. 18 c, as compared to the non-ghosted image 802 of FIG. 18 b, wouldalso make the recorded pixels of detected light energy by the sensors 84(FIG. 5) somewhat less precise, thus less unique to the image 800 or 802than would be obtained by producing the image 800 or 802 on the SLM 26instead of the ghosted image 802′. However, this decrease in resolutioncapability can actually be turned to an advantage for search andcomparison applications, where near matches as well as matches aredesired. As illustrated in FIG. 18 c, the initial edge image pattern 802is bright, the nearest ring of ghost edge images 802 _(A) is lessbright, the next ring of ghost edge images 802 _(B) is even less bright,and the outermost ring of ghost edge images 802 _(C) is less bright yet.However, the ghost images 802 _(A), 802 _(B), 802 _(C) increase thespatial frequency of the image 802′, thus cause more radial dispersionof the light energy bands 34 in the FT optic pattern 32. Consequently,the portions of the light energy bands 34 that originate from theinitial edge image 802 in the center of the ghosted pattern 802′ arebrighter, i.e., more intense, than portions of the light energy bands 34that originate from the ghost images 802 _(A), 802 _(B), 802 _(C).Therefore, while more sensors 84 of the detector array 82 will detectlight energy reflected by the segmented radial SLM 50 to the detector 80for a ghosted image 802′, the sensors 84 that sense the highestintensity (I) light energy will be the sensors 84 that correspond to theinitial edge image 802, and those intensities can be recorded and storedfor future access, analysis, searching, matching, and/or retrieving, asdescribed above. The lesser intensities detected by other sensors 84 forlight energy emanating from the nearest ring of ghost images 802 _(A)are also recorded and stored, as are those even lesser light intensitiesemanating from the other rings of ghost images 802 _(B), 802 _(C) sensedby still other sensors 84. Therefore, in a search and matching processwith other images, matches to the brightest or highest intensities ofboth images would indicate the highest probability that the respectiveimages are the same. If no such match can be found to the brightest orhighest intensity pixels, RIXels, RIXSels, or other records of opticpatterns that are characterized as described above, then comparisons tolesser intensities corresponding to ghost images 802 _(A), 802 _(B), 803_(C) can be attempted to find near matches.

The ghosting process is quite simple and can be scaled to achieve adesired result. Essentially, a software program can simply be applied toreproduce each pixel of an image at selected locations, at selecteddistances, and at selected angular orientations in relation to suchpixel, as illustrated in the simple example of the dot 800 in FIGS. 18a–c. An example of this ghosting process in a slightly more compleximage 810 in the shape of a house is illustrated in FIGS. 19 a–c. Theedges of the uniform or featureless areas of the house image 810 arefound and produced in an edge image 812, which maintains the shapecontent of the image 810, as explained above. Then the ghosting processdescribed above is applied to the edge image 812, as illustrated in FIG.18 c, to create ghost images 812 _(A), 812 _(B), 812 _(C), et seq., atselected distances, angular orientations, and decreasing brightnessesthe farther the ghost images 812 _(A), 812 _(B), 812 _(C) are from theinitial edge image 812.

The ghosting process of this invention can also be applied to images forwhich edges have not been found or produced, as described above.However, more pixel processing by the computer 20 or other processorwould be required, and resulting shape resolution may not be as sharp.

Since these and numerous other modifications and combinations of theabove-described method and embodiments will readily occur to thoseskilled in the art, it is not desired to limit the invention to theexact construction and process shown and described above. For example,Accordingly, resort may be made to all suitable modifications andequivalents that fall within the scope of the invention as defined bythe claims which follow. The words “comprise,” “comprises,”“comprising,” “include,” “including,” and “includes” when used in thisspecification and in the following claims are intended to specify thepresence of stated features or steps, but they do not preclude thepresence or addition of one or more other features, steps, or groupsthereof.

1. A method of characterizing an image for shape content, comprising:producing a Fourier transform optic pattern of the image with lightenergy; spatial filtering the light energy from the Fourier transformoptic pattern by selecting light energy from discrete portions of theFourier transform optic pattern at a plurality of discrete angularorientations and separating such discrete portions from other portionsof the Fourier transform optic pattern to create a plurality of filteredFourier transform patterns of light energy from those discrete portions;projecting the light energy of the filtered Fourier transform patternsinto spatial domain images of shape content; detecting intensities oflight energy as it is distributed in the spatial domain images of shapecontent for the respective angular orientations; and storing theintensities of light energy detected in the spatial domain images ofshape content along with the respective angular orientations.
 2. Themethod of claim 1, wherein spatial filtering the light energy from theFourier transform optic pattern includes: focusing the Fourier transformoptic pattern onto an active optic area of a spatial light modulator;selecting light energy from the discrete portions of the Fouriertransform optic pattern at a plurality of angular orientations forseparation by selectively activating portions of the spatial lightmodulator at selected angular orientations to rotate plane ofpolarization of the discrete portions of the light energy of the Fouriertransform optic pattern; and separating the light energy with therotated plane of polarization from light without the rotated plane ofpolarization.
 3. The method of claim 2, including selectively activatingportions of the spatial light modulator at selected segments positionedin said angular orientations and at and different radial distances withrespect to an optic axis of the Fourier transform optic pattern.
 4. Themethod of claim 2, including selectively activating portions of thespatial light modulator to rotate plane of polarization of light energyin the Fourier transform optic pattern that is incident on selectedsectors of the active optic area of the spatial light modulator thatextend radially in discrete angular orientations with respect to anoptic axis of the Fourier transform optic pattern.
 5. The method ofclaim 4, including selectively activating portions of the spatial lightmodulator to rotate plane of polarization of light energy in the Fouriertransform optic pattern that is incident on selected segments of theselected sectors to produce shape content in the spatial domain imagesthat corresponds in angular orientation to the angular orientations ofthe sectors with respect to the optic axis and that correspond inspatial frequency to radial positions of the selected segments withrespect to the optic axis.
 6. The method of claim 5, including:detecting intensities of light energy as it is distributed in thespatial domain images of shape content for the respective angularorientations of the selected sectors and for the respective radialpositions of the selected segments of the selected sectors; and storingthe intensities of light energy detected in the spatial domain images ofshape content along with the respective angular orientations and alongwith the respective radial positions.
 7. The method of claim 6,including: detecting the intensities of the light energy as it isdistributed in the spatial domain images of shape content by focusingthe spatial domain images of shape content on an array of photodetectorelements that are capable of detecting intensities of light energyincident on such elements and of producing signals that are indicativeof the respective intensities of light energy detected by the respectiveelements for pixel portions of the spatial domain images of shapecontent; and storing the intensities (I) of light energy detected in thepixel portions of the spatial domain images of shape content as detectedby the photodetector elements in the array for each angular orientation(R) and for each radial position (S), including positions of therespective pixel portions where such intensities (I) are detected. 8.The method of claim 1, including: producing a plurality of ghost imagesaround the image that is being characterized, each ghost image havingshape content that is substantially the same as the image beingcharacterized; and producing the Fourier transform optic image from theghost images along with the image being characterized.
 9. The method ofclaim 6, including producing the ghost images with each ghost imagehaving less light energy than the image being characterized.
 10. Themethod of claim 6, including replicating original pixels that comprisethe image being characterized and offsetting each such replicated pixelfrom its corresponding original pixel by an equal distance and angularorientation to the original pixel to create a ghost image.
 11. Themethod of claim 8, including dispersing the plurality of ghost images ina symmetrical manner around the image being characterized.
 12. Themethod of claim 6, including: finding edges of the shape content in theimage being characterized an edge image of the shape content;replicating original pixels that comprise the edge image; and offsettingeach such replicated pixel from its corresponding original pixel by anequal distance and angular orientation to the original pixel to create aghost image.
 13. The method of claim 10, replicating the pixels thatcomprise the ghost image with less light energy than the correspondingpixels of the edge image.
 14. An optical image shape content analyzer,comprising: a Fourier transform lens having a focal point in focal planeat a focal distance; a spatial light filter comprising: (i) a filterspatial light modulator that has an active optic area around a centralaxis positioned in the focal plane of the Fourier transform lens withthe central axis coincident with the focal point, said active optic areacomprising discrete active optic components that are capable ofselective activation to selectively rotate or not rotate plane ofpolarization of light incident at various angular orientations inrelation to the central axis; and (ii) a polarization analyzer that iscapable of separating light polarized in one plane from light polarizedin another plane; an image producing spatial light modulator with anassociated light source, wherein the image producing spatial lightmodulator is addressable to produce an image in an optic pattern withlight from the associated light source, said image producing spatiallight modulator being positioned to project such an image optic patternof light through the Fourier transform lens to form a Fourier transformoptic pattern of the image optic pattern at the focal plane of theFourier transform lens; and a photodetector positioned to receive lightfiltered by the spatial light filter, said detector including an arrayof sensors that are capable of detecting filtered patterns of lightenergy intensities in the filtered light.
 15. The optical image shapecontent characterizer of claim 14, wherein the discrete activecomponents are disposed in the active optic area in a manner thatextends radially outward at various angular orientations in relation tothe central axis.
 16. The optical image shape content characterizer ofclaim 15, wherein the discrete active components comprise individualsectors of the active optic area.
 17. The optical image shape contentcharacterizer of claim 16, wherein the discrete active componentscomprise individually addressable segments of the sectors.
 18. Theoptical image shape content characterizer of claim 17, wherein theindividually addressable segments are disposed radially in relation tothe central axis to form the active optic sectors.
 19. The optical imageshape content characterizer of claim 15, wherein the discrete activecomponents comprise rectangular components extending radially inrelation to the central axis.
 20. The optical image shape contentcharacterizer of claim 15, wherein the active optic area comprises arectangular spatial light modulator array of active optic elements andthe discrete active components comprise active optic elements of arectangular array of such elements that are activatable in distinctgroups of such elements that extend radially outward in relation to thecentral axis.